Estimation of Absorbed Dose of Uterus and Thyroid in Women Based on Scan Center Dose in Radiation with DEXA Pencil-beam System

Dual energy X-ray absorptiometery (DEXA) is presently considered as the standard technique for diagnosis of osteoporosis. Since there is still no evaluation based on the correlation between scan center dose and critical organs doses, in this study after measuring surface doses of thyroid and uterus as critical organs the correlation between scan center dose and thyroid and uterus surface doses were calculated in order to assess the rate of radiation doze to patients. In this study, 40 women underwent bone densitometry of Lunar DPX-MD system with pencil beam in two scan modes of AP spine and femur, simultaneously. Then surface doses of thyroid, uterus, scan center, and background were measured by placing 433 TLDs-400 at the surface of thyroid and uterus and also scan center. Then correlation between scan center dose and critical organs surface dose were analyzed and regression functions with significant level were determined. In AP spine and femoral scanning, average surface doses of thyroid (91 TLD-400) and uterus (84 TLD-400) were 1.88±1.36 and 1.81±1.03 µGy, respectively. Scan center dose in this scanning mode was 5.70±2.38 µGy. There was significant correlation between surface doses of thyroid and uterus and scan center dose. Therefore, regression functions and correlation coefficients were calculated. The observed significant correlation between critical organs surface dose and scan center dose showed that Lunar DPX-MD with pencil beam has very low radiation, similar to background doses.